Thursday, May 26, 2016

Indoor pool
environments are humid places by design, but, in the opinion of Dectron's James
Hogan, far too many suffer from excessive humidity, which manifests itself in
the form of foggy windows, premature degradation or outright rotting of
building materials, and just plain stinky and steamy air.

Homeowners who've built these indoor
pools tend to get a little steamed themselves when their natatoriums (just a
fancy word for indoor pools) get this way, and it's usually the builder that
bears the brunt of that frustration.

"Pool builders typically aren't
the reason for dysfunctional indoor residential pools, but they're usually the
ones that get blamed," says Hogan, a product development engineer and CPO
in Dectron International's Roswell, Ga., office.

Builders without a lot of
familiarity with indoor pools might deserve part of the blame, but there's
usually blame enough to share with the architects, mechanical contractors and
the homeowners themselves when projects go awry.

"These principles work
synergistically in an indoor pool environment. A deficiency in one part affects
all the other parts and thus the entire project. The pool builders should keep
a watchful eye on each indoor pool project, from the design and construction
phase through culmination."

Architecture
And Construction

Tim O'Neil is the operations manager
and construction engineer for Downes Swimming Pool Co., in the Chicago suburb
of Arlington Heights. He and his crew do an average of two indoor pools per
year, always residential and always elaborate. And while his projects don't end
up like so many others, he does see problems in many hotel pools he's called in
to troubleshoot.

"When I get a call from a hotel
or something like that, they just call me out of exasperation," he explains.
"I come out and I look, and the amount of mis-engineering and installation
errors and cutting of corners for these indoor installations just astounds me.

"The pool is usually a toxic,
humid, molded, rotted mess. That's because rules weren't followed when it was
built and corners were cut because they were worried about putting a $100,000
gold baluster in front of the building instead of spending the extra 10 grand
in the pool room."

These problems arise from mechanical
engineers and architects who aren't familiar with building indoor pools as
often as they do from willful negligence, according to Keith Coursin, president
of Desert Aire, a manufacturer of dehumidification systems in Germantown, Wis.

"One of the things that I've
seen is that so many of these architects and mechanical engineers design for
regular living spaces," he explains. "Everybody thinks about normal
environments, and they forget that the aquatic environment is year-round at a
nominal 85 degrees and in the 60 degree dew points.

"I always try to paint the
picture for most people that an indoor pool is like your worst dog days of
August. It's hot and humid. So when you think about it in those terms, that's
your inside condition, what are you going to do differently about your choice of
materials?"

Vapor barriers are an area where
poor choices are often made. Sometimes they're installed incorrectly; sometimes
they're not installed at all. The vapor barrier, which can be a plastic sheet,
foil-backed or extruded plastic sheet, or a vapor-retardant paint coating,
should envelop the entire pool room and is critical in preventing condensation
which can rot wood, corrode metal and result in concrete spalling and mold and
mildew problems.

"You want a very heavy
polyethylene sheeting. You want the heaviest mil you can get in a
plastic," says O'Neil. "And the application of that vapor barrier is
also very important. If you're just hitting it with a staple gun, you're
putting all kinds of little holes in it. What you want to use is something like
a hand-applied roofing nail so you're not punching the staples right through
the plastic.

As for the material that covers the
vapor barrier, O'Neil is partial to cedar, which is resistant to water to begin
with, and, when applied over a good vapor barrier, eliminates a lot of issues
with degradation caused by humidity. Not all projects are specified this way,
however.

"We've seen people using
standard drywall," Coursin says. "You've got to use greenboard, which
contains an oil-based additive, if you're going to use drywall. It's got to
withstand that moisture-laden environment."

Windows

Most pool rooms will have some
windows, and it's important to choose ones that will hold up to the severe
environment of a natatorium, according to Coursin.

"I wish I had a buck for every single-pained window I've seen used on an indoor pool," he says. "Your
dew point is going to be reached, and you are going to have condensation. I've
been to job sites where the condensation has gotten to the wood frames, which
weren't sealed by the way, and they've literally pushed the glass together and
shattered it."

Windows should be dual or triple
paned to cut down on condensation. Choose a less-expensive window, and you'll
need to pay closer attention to air distribution in the room.

Moving
Air

The second critical factor in a
well-designed and properly built indoor pool environment is air distribution, a
job handled by large dehumidification systems. These systems work a lot like
super-charged air conditioners, except that they discharge warm, dry air
instead of chilled air and are designed to handle much larger humidity loads.

But these systems in themselves
aren't going to eliminate poor air quality and damage to the physical
environment surrounding the pool if the dehumidified air isn't directed where
it should be.

"That, to me, is really the
key," says Coursin. "Now, the first and most obvious place that needs
warm, dry air, which is what comes off the dehumidifier, is the windows. It is,
by far, the weakest link of any construction material that you can put in a
pool room.

"So you have to design your
distribution network to flush the outside windows. Now, if you're talking about
a building that's all glass, well, that's a difficult job. If you talk about
only one wall, OK, you can design the duct work pretty readily to flush that
one wall of windows."

Getting the air where it needs to be
is especially important in colder climates, where the exterior temperature can
bring windows and exterior walls down below the dew point in the room, usually
between 60 and 70 degrees Fahrenheit, unless warm dry air is spread evenly
across them. Rooms with high humidity have high dew points, making the moisture
in the air condense into water. Keeping surfaces warm helps prevent this from
happening, according to Hogan.

"Diffusers should be arranged
to direct air at a sharp angle to the surfaces, and you need them close to the
surfaces," he explains. "If you shoot the dehumidified air directly
against the walls or windows, it just bounces back and doesn't work. If the
fluid flow is at a sharp angle, it'll kind of stick to the surface.

"The air distribution should
produce 10 to 50 feet per minute of airflow across the pool surface, but should
not blow air directly onto the pool surface. That's counter-productive and
causes evaporation."

The other side of the airflow
equation is the return air, and there are a number of different ways to situate
the duct-work.

"For many years, the standard
practice said, 'Hot, humid air rises, therefore I want my return air up at the
ceiling level,'" Coursin explains. "But there's a new discussion
going on within the engineering community that says a portion of the return air
should be done down lower by the pool itself to help bring the air over the
pool to remove the off-gassed chemicals."

As is the case with other aspects of
indoor construction, duct work is often given too little thought. And sometimes,
this thoughtlessness leads to major problems.

O'Neil says he's seen return ducts
located near the floor (away from the humid air) and even diffusers located
near the ceilings, blowing air directly at the surface of the pool instead of
at the exterior walls.

"That's pretty stupid," he
says. "So they're taking dehumidified air, which is dry, and blowing it at
the surface of the pool. What do you think is going to happen? It evaporates
the water really, really well."

The best airflow designs are planned
before construction even begins, Hogan says, using computational fluid dynamics
(CFD), a computer modeling system that checks for proper air distribution long
before groundbreaking.

Equipment

All the careful work builders,
mechanical engineers and architects do on material selection, fluid dynamic
evaluation and careful duct placement isn't going to head off potential
problems if the right dehumidification system isn't chosen.

According to Hogan, you've got to
consider the size of the room, the outdoor temperature, the materials in the
room. But that's not enough. You've also got to know how the homeowners plan to
use the room. Where will they keep the air temperature? What about the water?
These two factors are critical in calculating the size and strength of the
dehumidifier that's needed, Hogan says, and once those decisions are made,
there's little room for making changes.

"Dehumidifier sizing is very
dependent on the homeowners' projected use of the pool," Hogan says.
"A common design includes a two-degree temperature differential between
the air and water - 84-degree air, 82-degree water. Homeowner preferences that
deviate from this standard - 75-degree air and 90-degree water, for example -
will significantly affect evaporation rates and dehumidifier sizing
calculations. But they're easily accommodated at the design stage.

"But the homeowner should know
that air and pool water temperature set point are locked together after the
equipment is ordered."

This tight correlation between
equipment size, customer use and material selection underscores the need to get
manufacturers and local reps involved in the early planning stages.

Chemistry
Matters

The final piece of the indoor pool
puzzle is pool water chemistry. It's the simplest piece of the puzzle, but like
all the other elements, neglect to pay it proper attention and the entire
project will suffer.

Hogan stresses the importance of
keeping pool chemicals out of the mechanical room (a common sin) or in an
unventilated closet to prevent damage to equipment.

"Whether the builder, the owner
or others perform aftermarket pool water testing, a DPD or FAS-DPD pool water
test kit should be used in order to determine the combined chlorine
levels," Hogan says. "The pool builder should set up a maintenance
schedule that includes water chemistry as well as a check for the mechanical
system's vital signs such as filters, belts and airflow.

"Not everyone is a CPO. It's
not hard, but you do need to pay attention to the chemistry. So compliance with
national standards and the CPO books is the best way to get long life out of
the mechanicals in the building.

"An indoor pool's building
envelope, mechanical equipment, water chemistry and air distribution all work
together to provide a properly functioning and healthy environment for the
user."

The synergistic relationship among
these elements requires strict attention to detail, careful planning at the
initial stages and the expert advice of a professional dehumidification
equipment manufacturer. There are, of course, easier, faster and cheaper ways
of putting in an indoor pool, but builders like O'Neil recommend against them.

"Don't be cheap when you're
putting an indoor pool in. If you're going to cut corners, don't put it
in," he says. "A cheap pool is a bad pool. It really is. And the cost
between doing things right and doing them wrong is probably 10 percent. "It's more important to pay attention to
what you're doing